A bumpy overseas trip and a month of pummeling by Democratic ads depicting Mitt Romney as an out-of-touch plutocrat and possible tax evader appear to have taken a toll.

Three polls released in the last 24 hours show President Obama widening his lead over the former Massachusetts governor to as much as nine points. The surveys of registered voters, all conducted sometime between Aug. 2 and 8, also have Romney’s unfavorable ratings headed north. Two of the polls show his support among independents slipping.

A Fox News poll found the largest deficit, with Romney trailing by nine points (49 percent to 40 percent) That’s the widest gap Fox has reported all year. Its July survey had Obama up by four points (45 percent to 41 percent). Fox found that Obama’s increasing advantage comes mainly on the strength of a big bump from independents, who now support the president by 11 points, up from four points in July.

Twenty-six percent of voters described themselves “extremely” or “very” comfortable with the prospect of a Romney presidency, while 71 percent said they were either “somewhat” or “not at all” comfortable. Forty-one percent were extremely or very comfortable with a second Obama term, while 59 percent fell into the somewhat or not-at -all categories.

A new CNN/ORC International survey placed the race at seven points (52 percent to 45 percent), up from 49 percent to 46 percent in July. Among independents, Obama’s lead is at nine points. Fifty-two percent of independents view Romney unfavorably, up from 40 percent in May. Sixty-four percent of all voters think he favors the rich over the middle class.

Voters also appear to be losing confidence in Romney’s ability to fix the economy, according to the CNN poll. Forty-five percent said they thought it would improve under Romney, down from 50 percent in May.

Romney’s overseas trip late last month was marked by misadventures. British leaders were miffed when he questioned their preparedness for the Summer Olympics. In Israel, he infuriated Palestinians by saying “culture makes all the difference” when looking at their lack of economic growth relative to the Israelis.

At home, the Obama campaign hammered on Romney’s business career at Bain Capital, with one ad showing images of closed factories and news stories about his foreign investments, accompanied by his off-key rendition of “America the Beautiful.” Another spot, addressing Romney’s refusal to release additional years of income tax returns, asks, “What is Mitt Romney hiding?”

A senior Romney adviser downplayed the new polls at a news briefing Friday morning, saying that they must be midsummer flukes because there had been no “precipitating event” to move the numbers so much. The campaign cited the latest Gallup tracking poll, which has the two candidates in a dead heat at 46-46 percent. Rasmussen, an automated poll that usually leans Republican, has Romney ahead 47-43 in its daily tracking.

One encouraging data point for Romney from the CNN poll: He continues to solidify his party’s support. Fifty-six percent of Romney voters said they strongly support him, up from 47 percent in May.

The poll results only raise the stakes surrounding Romney’s forthcoming vice-presidential rollout and the opportunity to reintroduce himself to the country at the Republican National Convention in Tampa this month. Presidential nominees usually enjoy a bounce in the polls immediately following the convention.

Among the possible vice-presidential selections, Republicans and GOP-leaning independents expressed a marked preference for Sen. Marco Rubio (Fla.) and New Jersey Gov. Chris Christie in the CNN survey. Both were viewed favorably by at least 50 percent. Former Minnesota governor Tim Pawlenty had a favorable rating of 37 percent, with 52 percent either having no opinion or saying they’d never heard of him. Sen. Rob Portman (Ohio) was even more of a question mark. Twenty-nine percent viewed him favorably, but 66 percent had no opinion or didn’t know who he was.

The new Reuters/Ipsos poll has Romney trailing Obama 49 percent to 42 percent, up a tick from the six-point spread last month. This comes despite continuing voter pessimism about the country’s condition, Reuters reported. Only 31 percent said the country was moving n the right direction, the lowest proportion since December 2011. Reuters did not report any findings on independents.

Philip Rucker in Boston contributed to this article.